In a storage system comprising multiple storage controllers, the access method from an operation server utilizing the storage system includes an active-standby method and an active-active method. In the active-standby method, only one active storage controller receives an access request from the operation server utilizing the storage system. On the other hand, in the active-active method, any storage controller may receive the access request from the operation server.
Although the processing for the access request from the operation server is complicated, demand for the active-active storage system is apt to increase for advantages of the active-active method such as that load applied to the storage controller is distributed and a failure may be restored promptly.
As for the volume switching, a technique is known that suppresses exhaustion of the in-host ID by switching an access request for a switching source volume to a switching destination volume with reference to a switching table that associates the in-host ID of the switching source volume and the in-storage ID of the switching destination volume with each other.
Also, a technique is known that executes a first remote copy on the storage basis in the normal state, and when a failure occurs in the first remote copy, enables failure handling by switching to a second remote copy on the host basis while suppressing the load to the host.
Further, a technique is known that, when an I/O request to a first volume out of a pair of volumes of the remote copy is failed, transmits the I/O request to a second volume to update the second volume and thereby improve the availability of the system.
As examples of the related techniques, Japanese Laid-open Patent Publication Nos. 2006-309638, 2006-285919, and 2009-266120 are known.